Regenerate kitchen-sink protos with pinned tool versions

Previous regen used local protoc/protoc-gen-go (32.1 / 1.36.11), which
churned the generated files. Re-run with the versions pinned in
versions.env (protoc 25.1 via mise, protoc-gen-go v1.31.0).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: stephanos